MX2014003315A

MX2014003315A - Oxygen application in claus units charged with an additional load -particularly a waste-gas stream containing so2 and coming from adsorbent regeneration.

Info

Publication number: MX2014003315A
Application number: MX2014003315A
Authority: MX
Inventors: Bernhard Schreiner
Original assignee: Linde Ag
Priority date: 2013-03-28
Filing date: 2014-03-19
Publication date: 2014-09-29
Also published as: US20140294719A1; RU2014111794A; EP2784022A1; ZA201402303B; EP2784022B1; PL2784022T3; US8900544B2; RU2653124C2; BR102014007518A2; DK2784022T3; PT2784022E; ES2545523T3; HUE025202T2; CN104073288A

Abstract

The present invention relates to a method removing sulphur from a fluid, comprising the steps of: - providing a first fluid comprising a sulphur-containing compound, - adsorbing the sulphur of said sulphur-containing compound onto an adsorbent, particularly in presence of hydrogen, - regenerating said adsorbent by oxidation of said adsorbed sulphur to sulphur dioxide thereby yielding an off-gas stream comprising sulphur dioxide, - providing a second fluid comprising hydrogen sulphide, - using said second fluid and said off-gas stream as reactants in a Claus process for producing elemental sulphur, wherein a part of hydrogen sulphide provided by said second fluid is oxidized to sulphur dioxide and water at an reaction temperature, wherein the residual hydrogen sulphide, the resulting sulphur oxide and said sulphur oxide provided by said off-gas stream are converted to elemental sulphur, wherein the oxygen required for said oxidation of said hydrogen sulphide provided by said second fluid is provided by an air stream, and wherein said off-gas stream dilutes said second fluid in said Claus process. According to the invention, it is provided that the Claus process is enriched with oxygen for maintaining said reaction temperature equal to or above 1100 DEG C.

Description

APPLICATION OF OXYGEN IN CLAUS UNITS CHARGED WITH A PARTICULARLY ADDITIONAL LOAD A WASTE GAS CURRENT CONTAINING S02 AND COMING FROM THE REGENERATION OF ADSORBENT Description of the invention The present invention relates to a method for removing sulfur from a fluid.

Such a method comprises the steps of providing a first fluid comprising a sulfur-containing compound, adsorbing the sulfur of the sulfur-containing compound on an adsorbent, in particular in the presence of hydrogen, regenerating the adsorbent by oxidation of the sulfur adsorbed to the sulfur dioxide. sulfur thereby producing an off-gas stream comprising sulfur dioxide, providing a second fluid comprising hydrogen sulfide, using the second fluid and the gas discharge stream as reagents in a Claus process to produce elemental sulfur, in where a part of hydrogen sulfide provided by the second fluid is oxidized to sulfur dioxide and water at a reaction temperature, and wherein the residual hydrogen sulfide, the resulting sulfur oxide and the sulfur oxide provided by the stream of output gas becomes elemental sulfur, and where the oxygen required for the oxidation of the sulfur Ref. 246896 of hydrogen provided by the second fluid is provided by an air stream, and wherein the gas stream dilutes the second fluid in the Claus process.

Sulfur recovery units based on the so-called "Modified Claus process" produces elemental sulfur from feed gases with high concentration of H2S by partial oxidation of the latter using air as the primary oxidant. This oxidation of air is done by applying an open flame inside a combustion chamber (also called Claus furnace). The feeds of Claus units operated in oil refineries are typically gas streams that have a high concentration of H2S (in this case, acid gas) sometimes combined with a second stream of so-called acidic water separator gas containing H2S and amounts greater than ammonia (NH3).

The stability of any flame based on fuel combustion is highly dependent on the concentration of flammable products within the fuel stream, in this case the most diluted fuel with compounds that do not participate in the oxidation process is the lowest temperature of the flame. In the extreme case the flame may even expire. In case of inerts like nitrogen this effect is more evident, but if S02 is imported in a Claus oven the complication is still aggravated by a second effect - that is, even less of the main fuel (eg, H2S) can be oxidized to S02, which is the important reaction partner of residual H2S within the sections downstream of the Claus unit. Therefore, in cases of import of gases containing S02 in a Claus furnace the natural consequence is one - under still substantial circumstances - drop in furnace temperature. The side effects of such a decrease in temperature are widely known.

The most notorious is the incomplete destruction of the so-called trace compounds as persistent hydrocarbons (benzene, toluene, xylenes, styrene) and also NH3. A discovery of hydrocarbons leads to fouling / deactivation of the catalyst and reduced sulfur quality. Even more sensitive to the reduction of furnace temperature is the destruction efficiency of NH3. If the latter is incomplete NH3 accumulates solid salts in "cold spots" of the Claus section downstream, which may lead to effects such as low sulfur recovery efficiency, plus plant downtime, considerable damage due to corrosion, reduced plant capacity, etc.

On the basis of this background, it is the object of the present invention to provide an efficient method and economic for the elimination of sulfur.

The problem is solved by a method having the features of claim 1.

According to the same, the Claus process is enriched with oxygen to maintain the reaction temperature equal to or higher than 1100 ° C, preferably higher than 1200 ° C, preferably higher than 1250 ° C, preferably higher than 1300 ° C, preferably higher than 1400 ° C.

A fluid in the sense of the present invention particularly refers to a liquid or a gas. The enrichment with oxygen of the Claus process leads to an improvement in the oxidation of hydrogen sulphide and an increase in the reaction temperature.

A further advantage of the method of the invention is that the dilution is compensated by the oxygen enrichment of the Claus process. Because the Claus units are limited in their gas flow rate by design, a dilution of the hydrogen sulfide fed decreases the capacity of the unit. In this way the yield of elemental sulfur decreases, because less hydrogen sulfide is oxidized and later converted to elemental sulfur. Due to the enrichment of the air stream with oxygen, the volume of the air stream can be decreased and a greater volume of hydrogen sulfide can be fed into the Claus unit / Claus process thus increasing the capacity of the Claus unit / Claus process.

Another advantage of the method according to the invention is that the hydrocarbons optionally present in the exhaust gas stream, for example, due to insufficient oxidation, in particular in the case of malfunction, such as an inadequate supply of air used for the oxidative regeneration of the adsorbent, are oxidized in the Claus process at the reaction temperature described above and thereby eliminated.

In some modalities, the Claus process is fed with air enriched with oxygen or directly with pure oxygen. Air enriched with oxygen in the sense of the present invention refers particularly to air with an oxygen content of at least 21% (v / v), 28% (v / v), 45% (v / v), 60 % (v / v) or 75% (v / v). Pure oxygen in the sense of the present invention relates in particular to oxygen with a purity of at least 90% (v / v). The use of air enriched with oxygen or pure oxygen allows a greater conversion of hydrogen sulfide in the second fluid in the same unit and avoids unwanted side reactions and contamination with nitrogen. In addition, the use of air enriched with oxygen or pure oxygen allows the processing of a second fluid with a low content of hydrogen sulfide (particularly below 20%). (v / v) of H2S) and / or a second fluid comprising ammonia, hydrocarbons, in particular methane or arenos such as benzene, toluene, xylene and styrene.

According to one embodiment of the present invention and in contrast to the normal Claus operations, not one third but less than one third of the hydrogen sulphide is converted to sulfur dioxide, which then reacts with the sulfur dioxide provided by the current from gas discharge to elemental sulfur.

According to one embodiment of the present invention, the conversion of hydrogen sulphide and sulfur dioxides is carried out in the presence of a catalyst.

According to one embodiment of the present invention, the catalyst comprises aluminum oxide or titanium oxide.

According to one embodiment of the present invention, the adsorbent is a reduced metal, a metal oxide or a mixed metal oxide, or a reduced metal combined with a metal oxide or a mixed metal oxide.

According to one embodiment of the present invention, the reduced metal is selected from zinc, nickel, iron and copper.

According to one embodiment of the present invention, the metal oxide is selected from zinc oxide, nickel oxide, iron oxide and copper oxide.

According to one embodiment of the present invention, the mixed metal oxide is selected from Zn-Fe-O, Zn-Ti-0 and Cu-Fe-Al-O.

According to one embodiment of the present invention, the first fluid is selected from the group consisting of crude synthesis gas and a stream of hydrocarbons.

According to one embodiment of the present invention, the hydrocarbon stream is a distillate of crude oil or product of crude oil, natural gas or biogas.

According to one embodiment of the present invention, the sulfur-containing compound is selected from the group consisting of hydrogen sulfide, a mercaptan, a thioether, a dithioether, a substituted or unsubstituted heteroarene, COS and CS2.

According to one embodiment of the present invention, heteroarene is selected from thiophene and its derivatives, such as, for example, benzothiophene and dibenzothiophene.

According to one embodiment of the present invention, the sulfur contained in the first fluid is adsorbed to the adsorbent in the presence of hydrogen in the case of the sulfur-containing compound is not hydrogen sulfide.

According to one embodiment of the present invention, the first fluid is adsorbed to the adsorbent in the absence of hydrogen in the case of the sulfur-containing compound is hydrogen sulfide.

According to one embodiment of the present invention, the second fluid is an acid gas from an acid gas removal process, particularly from the treatment of amine gases.

According to one embodiment of the present invention, the second fluid further comprises ammonia or a hydrocarbon, wherein the ammonia is converted to nitrogen and water and the hydrocarbon is oxidized to carbon dioxide and water under the reaction conditions in the thermal section of the Claus process, in particular at the aforementioned reaction temperature above 1100 ° C.

According to one embodiment of the present invention, the hydrocarbon comprised within the second fluid is a light alkane, an olefin or an aromatic compound such as for example benzene, toluene, xylene or styrene.

As an advantage of the present invention, the conversion of ammonia to nitrogen at the reaction temperature prevents the formation of solid ammonia salts in cold spots of the Claus section downstream of the Claus furnace.

As another advantage of the present invention, the complete oxidation of the hydrocarbon prevents fouling or deactivation of the catalyst described above.

According to one embodiment of the present invention, the first fluid comprising the sulfur-containing compound or compounds is hydrogenated, wherein the compound or Sulfur-containing compounds are reduced to hydrogen sulfide and a residue or residues of the corresponding compound thereby producing a fluid enriched with hydrogen sulfide, wherein the hydrogenation is carried out before adsorption.

According to one embodiment of the present invention, the hydrogenation is carried out in the presence of hydrogen.

The invention is further characterized, without limitation, by the following examples, from which other features, advantages or modalities may be derived. The examples do not limit but illustrate the invention, where Figure 1 shows an embodiment of the method according to the invention.

Figure 2 shows another embodiment of the method according to the invention; Y Figure 3 shows another embodiment of the method according to the invention.

Example 1: In oil refineries, a new process for the deep desulphurization of hydrocarbon streams 21 containing molecules carrying S has entered in recent years. This process (also referred to as S-Zorb), based on the reductive adsorption 12 of sulfur in a solid 26, leads - by the oxidative regeneration 13 of the adsorbent loaded by oxidation of air 32 - to an exit gas 27 comprising an appreciable but non-dominant amount of S02 (eg, 5 vol%). A detailed description of the S-Zorb process can be found in Song et al., Applied Catalysis B: Environmental 41 (2003), pages 207-238.

One way to get rid of this waste stream 27 is to send it to a Claus unit (or Claus process) 14, where all the components of this waste stream are present (N2, 02, CO, C02, lows, hydrocarbons), respectively , are produced inside the Claus furnace (S02, H2, CO, C02).

In case the waste stream mentioned above is fed into the Claus 14 unit it has to be assumed that the temperature in the Claus furnace can drop considerably and that the measurements may have to be taken to restore the operating stability and / or destruction of sufficiently efficient traces.

A particularly crucial feature can be seen in the S-Zorb output gas operation 27 by sending in a Claus 14 unit and the combination of this procedure measurement with the application of oxygen 33 (for example, oxygen enrichment 33 of the section or thermal step of Claus) in order to maintain the temperature of the oven at an appropriate level.

The method according to the invention provides among others the following advantages: Disposing of a current of waste 27 comprising S02 in a manner benign to the environment - in this case, in a way that the sulfur of the S02 molecules is recovered in elementary and therefore useful form 34; and by oxygen enrichment 33 to guarantee the appropriate conditions for a reliable and efficient operation of the sulfur recovery process (in this case, Claus 14 process).

A stream of hydrocarbons 21, preferably a distillate of crude oil, with a sulfur-containing compound such as a mercaptan, a thioether, a dithioether or a heteroarene such as thiophene or benzothiophene 12 is contacted with an adsorbent 26 in the presence of hydrogen 22 (cf Fig. 1). The sulfur atom adsorbs 12 on the adsorbent 26 and reacts with the adsorbent 26, whereby the sulfur atom is removed from the compound and is retained by the adsorbent 26. The adsorbent 26 can be any compound capable of forming sulfides and is preferably a reduced metal or metal oxide, which forms a metal sulfide when reacted with hydrogen sulphide. The spent sulfur hydrocarbon stream 24 is then processed further.

The loaded adsorbent is then regenerated by oxidation 13 with molecular oxygen, typically composed of air, producing an S02 rich in exhaust gas 27, and the regenerated adsorbent 26 is then retransferred to the process of adsorption 12. The adsorption 12 is generally carried out in a fluid bed reactor 12, in which the spent adsorbent 25 is continuously removed from the reactor 12 and transferred to a regeneration section 13. In the regeneration section 13 the sulfide is oxidizes outside the adsorbent 25 in the presence of air 32, and the cleaned adsorbent 26 is recycled back to the reactor 12. In case the adsorbent 25, 26 is a reduced metal the adsorbent 25 furthermore can be regenerated by reduction with hydrogen 22 This exhaust gas stream 27 is then sent in a Claus unit (or Claus process) 14. In the Claus unit 14, a hydrogen sulfide containing a second fluid 31 is processed, wherein a sulfide portion of Hydrogen is oxidized by air 32. The second fluid 31 can be any fluid comprising hydrogen sulfide, for example, acid gas from gas sweetening or other acid gas removal processes. Typically, a third of the hydrogen sulfide is converted to sulfur oxide which then reacts with the remaining two thirds of the hydrogen sulfide to elemental sulfur 34. Because the outlet gas stream 27 provides a certain amount of sulfur dioxide, Less than a third of hydrogen sulfide has to be oxidized.

The Claus 14 process is usually carried out in a Claus 14 unit consisting essentially of an oven that represents the thermal section of the Claus unit 14, where the hydrogen sulfide is oxidized, and a catalytic converter representing the catalytic section, where the converter is a reactor designed to facilitate the reaction of hydrogen sulfide and sulfur oxide to elemental sulfur 34. The converter may comprise a catalyst-containing bed such as aluminum oxide or titanium oxide. One or two additional catalytic converters are typically connected to a first catalytic converter. Before entering the catalytic converter the second fluid 31 can be heated again above 200 ° C by appropriate means to heat such a heat exchanger. The formation 14 of elemental sulfur 34 can, to a certain degree, already occur in parallel to the oxidation reaction 14 in the furnace.

The elemental sulfur 34 can be removed in a condenser, where the sulfur vapor 34 is condensed to liquid sulfur 34. The sulfur vapor 34 can be further cooled in the condenser below 140 ° C. Additionally, a condenser may be disposed between the furnace and the catalytic converter.

By sending the exhaust gas 27 in the Claus unit 14, the reaction mixture consisting of the second fluid 31 and air 32 is diluted causing a drop in the reaction temperature and a decrease in the sulfide concentration of hydrogen in the reaction 14. Further, because a Claus unit 14 is generally limited by a gas flow rate, adding additional volumes decreases the volume and, therefore, the amount of hydrogen sulfide that can be converted. This negative effect is compensated by air enrichment 32 or directly the Claus 14 process with oxygen 33. The oxygen-33 enrichment supports the oxidation 14 of hydrogen sulfide resulting in a higher temperature and a higher sulfur conversion rate of hydrogen.

Particularly, the oxygen concentration of the air 32 is increased in such a way that the volume of the air 32 can be reduced, thus compensating for the dilution effect of the exhaust gas 27. In addition, the application of oxygen 33 of enriched air 32 in the process of Claus 14 ensures that a desired reaction temperature of at least 1,100 ° C is maintained, preferably a reaction temperature of at least 1250 ° C (see also above).

The second fluid 31 may further comprise trace compounds such as persistent hydrocarbons (e.g., benzene, toluene, xylenes, or styrene). The trace compounds are oxidized to carbon monoxide, carbon dioxide and water at temperatures above 1100 ° C, which prevents fouling / deactivation of the catalyst and reduced sulfur quality 34 caused by the trace compounds. The second Fluid 31 may also comprise ammonia, which is converted to nitrogen and water at temperatures above 1100 ° C. This conversion is almost completely complete at a temperature higher than 1250 ° and prevents the formation of solid accumulations and obstructions caused by ammonium salts.

Alternatively, hydrocarbon stream 21 can first be treated with hydrogen 22 in the presence of an appropriate catalyst such as Co-Mo / Al203 or Ni-Mo / A1203, whereby the sulfur-containing compound is reduced to hydrogen sulfide and a residual compound residue (see Fig. 2). After this, the resulting hydrocarbon stream 23 enriched with hydrogen sulfide is contacted with an adsorbent 26, wherein the hydrogen sulfide reacts with the adsorbent 26, and wherein the sulfur atom is retained by the adsorbent. The adsorption 12, the regeneration 13 and the supply of the resulting exhaust gas stream 27 to the Claus unit 14 is carried out analogously to the example described above.

Example 2: This concept is not only valid for residual flows from the S-Zorb process mainly applied in oil refineries. For gasification schemes, an adsorption process is already highly developed in order to carry out the desulfurization of hot gas. Here, also a residual gas is produced in the step of Adsorbent regeneration, which can be sent in a Claus unit.

Here, again, the combination with the application of oxygen is an elegant solution; get rid of S02 by recovering the sulfur. Also the removal of sulfur from other gas streams such as natural gas is a source for waste streams rich in sulfur dioxide, which can be processed as described above.

In the case of a hydrocarbon stream such as natural gas or another gas stream, such as crude synthesis gas already comprises hydrogen sulfide, the stream (21) is contacted directly with the adsorbent (Figure 3) without any preparation . Again, the adsorption 12, regeneration 13 and the resulting exhaust gas stream feed 27 to the Claus unit 14 is performed analogously to the examples described above.

List of reference numbers It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A method for removing sulfur from a fluid, characterized in that it comprises the steps of: providing a first fluid comprising a sulfur-containing compound, - adsorbing the sulfur of the sulfur-containing compound on an adsorbent, in particular in the presence of hydrogen, regeneration of the adsorbent by oxidation of the sulfur adsorbed to sulfur dioxide thereby producing an exhaust gas stream comprising sulfur dioxide, - providing a second fluid comprising hydrogen sulfide, - the use of the second fluid and the output gas stream as reagents in a Claus process to produce elemental sulfur, • where a part of hydrogen sulphide provided by the second fluid is oxidized to sulfur dioxide and water at a reaction temperature, • where the residual hydrogen sulphide, the resulting sulfur oxide and the sulfur oxide provided by the off-gas stream are converted to elemental sulfur, • wherein the oxygen required for the oxidation of the hydrogen sulfide provided by the second fluid is provided by an air stream, and • where the outlet gas stream dilutes the second fluid in the Claus process, where the Claus process is enriched with oxygen to maintain the reaction temperature equal to or greater than 1100 ° C, preferably higher than 1200 ° C, preferably higher than 1250 ° C, preferably higher than 1300 ° C, preferably higher than 1400 ° C.

2. The method according to claim 1, characterized in that the air stream is enriched with oxygen or the oxygen is directly fed to the Claus process.

3. The method according to any of claims 1 or 2, characterized in that the adsorbent is a reduced metal, preferably zinc, nickel, iron or copper, or a metal oxide, preferably zinc oxide, nickel oxide, iron oxide or copper oxide, or a mixed metal oxide, preferably Zn-Fe-0, Zn-Ti-0, or Cu-Fe-Al-0.

4. The method according to any of the preceding claims, characterized in that the first fluid is selected from crude synthesis gas and a stream of hydrocarbons, particularly a distillate of crude oil, a product of crude oil, natural gas or biogas.

5. The method according to any of the preceding claims, characterized in that the first fluid is hydrogenated, wherein the sulfur-containing compound is reduced to hydrogen sulfide and a corresponding compound residue, and wherein the hydrogenation is carried out before adsorption . SUMMARY OF THE INVENTION The present invention relates to a method for removing sulfur from a fluid, comprising the steps of: providing a first fluid comprising a sulfur-containing compound, - adsorbing the sulfur of the sulfur-containing compound on an adsorbent, in particular in the presence of hydrogen, regeneration of the adsorbent by oxidation of the sulfur adsorbed to sulfur dioxide thereby producing an exhaust gas stream comprising sulfur dioxide, - providing a second fluid comprising hydrogen sulfide, - the use of the second fluid and the gas stream as reagents in a Claus process to produce elemental sulfur, • where a part of hydrogen sulphide provided by the second fluid is oxidized to sulfur dioxide and water at a reaction temperature, • where the residual hydrogen sulphide, the resulting sulfur oxide and the sulfur oxide provided by the off-gas stream are converted to elemental sulfur (34), • where the oxygen required for the oxidation of the Hydrogen sulfide provided by the second fluid is provided by a stream of air, and • where the exhaust gas stream dilutes the second fluid in the Claus process, According to the invention, this provides that the Claus process is enriched with oxygen to maintain the reaction temperature equal to or higher than 1100 ° C.